South Korea's chief official on North Korea policy says he believes North Korea's recent acts of international defiance are aimed at shoring up power at home. With talks to end the North's nuclear weapons at a standstill, South Korea is intensifying its diplomacy with partners to respond to the North's latest threats.

North Korea's official Rodung Sinmun newspaper described the country as a "proud nuclear power" Monday, and warned it would be a "great mistake for the United States to think it will not be hurt" in the event of military conflict on the peninsula.

That latest example of shrill rhetoric from Pyongyang comes as the U.S. Navy tracks a North Korean vessel which may be carrying missile parts or other weaponry. Such items are prohibited under the latest United Nations Security Council resolution passed after North Korea's nuclear test last month.

South Korea's main 24-hour cable news channel network cited intelligence officials Monday as saying the North Korean vessel was probably destined for Burma.

Hyun says social instability has increased in North Korea, so leader Kim Jong-il needs to continue to reinforce his domestic power base.

Those comments echo earlier assessments by analysts here in Seoul, who say Kim Jong Il's apparent stroke about a year ago challenged perceptions of his complete command of the North's government.

Hyun adds, the North Korean leader also has to think about possible power succession, whether it happens right away or some time later-- that is another reason to reinforce his power base.

South Korea is intensifying diplomacy to contain North Korea's pursuit of nuclear weapons. President Lee Myung-bak travels to Tokyo this Sunday to discuss North Korea with Japanese Prime Minister Taro Aso. Seoul's main envoy on the nuclear issue, Wi Sung-lac, is scheduled to meet with his Russian counterpart in Moscow later this week. A South Korean envoy is also traveling to a gathering in Poland for the South's first formal participation in a U.S.-led anti-proliferation cooperative.